https://jsbin.com/xukike/edit?html,output
@hzmnet You need to use this.$$('#<id>') to find elements that generate dynamically.
Your issue and your jsbin are not very explicit.
Could you please give us a better example and more explanation about your problem?
If you want to find an element with its id you need to use this.$.<id>.
If you want to find an element with its name you need to use this.$$.('element-name').
You can also use Polymer DOM API to find an element through the shadow DOM.
I hope this answer will help you, if not I would be pleased to discuss with you about it if you give us more details.
This is a limitation of creation of the this.$ hash as described here: https://www.polymer-project.org/1.0/docs/devguide/local-dom#node-finding
Note: Nodes created dynamically using data binding (including those in dom-repeat and dom-iftemplates) are not added to the this.$ hash. The hash includes only statically created local DOM nodes (that is, the nodes defined in the element's outermost template).
Closing per above comment.
Most helpful comment
This is a limitation of creation of the
this.$hash as described here: https://www.polymer-project.org/1.0/docs/devguide/local-dom#node-finding